Medical guidewire

ABSTRACT

Provided is a guidewire including a core shaft, an outer flexible tube, a stranded wire that extends parallel to the core shaft, and a hollow stranded-wire coil disposed in the outer flexible tube. The hollow stranded-wire coil is formed of multiple strands and surrounds the distal end portion of the core shaft and the stranded wire. Distal ends of the hollow stranded-wire coil, the core shaft, and the stranded wire are joined to a distal end of the outer flexible tube.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a medical guidewire used for medicalpurposes such as inserting a catheter into a blood vessel, a ureter, oran organ or inserting an indwelling device into part of a blood vesselsuffering from an aneurysm.

2. Description of the Related Art

In general, it is required that a medical guidewire have a flexibledistal end portion. In order to fulfill such a requirement, a guidewire100 of the related art includes a core shaft 101 and a coil spring 102that surrounds the core shaft 101, and the diameter of a distal endportion 103 of the core shaft 101 is made small so as to improveflexibility (see FIG. 4).

When using the guidewire 100 to guide a device, such as a catheter or anindwelling device, to a target region in a human body, the distal endportion of the guidewire 100 may be unintentionally bent into a U-shape.For some operations, the guidewire 100 is bent into a U-shape beforeinsertion in order to prevent misinsertion of the guidewire 100 into anontarget blood vessel or in order that the guidewire 100 is securelyheld by a blood vessel wall by using the resilience of the guidewire100.

The guidewire 100 of the related art has a low rigidity because thediameter of the distal end portion 103 of the core shaft 101 is small,so that the guidewire 100 is easily bent due to stress concentration.Once the core shaft 101 is bent into a U-shape, plastic deformationoccurs, so that the core shaft 101 has a residual angle even after theU-shaped bending is released. Due to the presence of the residual angle,the operability of the guidewire 100 is reduced, and the guidewire 100may have to be replaced during the operation.

It is required that the guidewire 100 have a flexible and resilientdistal end portion, and it is also required that the guidewire 100 has agood torque transmission with which an operation performed at theproximal end portion is smoothly transmitted to the distal end portion.

A modification of the guidewire 100 uses a stranded wire as the distalend portion 103 of the core shaft 101 (see Japanese Unexamined PatentApplication Publication No. 2008-161491). The guidewire 100 has acertain degree of resilience after having been bent. However, when theguidewire 100 is bent into a U-shape having a large curvature, theguidewire 100 may not recover its original shape even after the U-shapedbending is released. Therefore, the drawback due to the presence of aresidual angle remains.

Another modification of the guidewire 100 includes a radiopaque innercoil disposed between the coil spring 102 and the core shaft 101 (seeJapanese Unexamined Patent Application Publication No. 08-173547 andJapanese Unexamined Patent Application Publication (Translation of PCTApplication) No. 2006-511304). With the guidewire 100, the rigidity of apart of the distal end portion 103 having the inner coil is increased.However, this modification also has the drawback due to the presence ofa residual angle after having been bent into a U-shape.

SUMMARY OF THE INVENTION

The object of the present invention, which has been achieved in order toovercome the drawback described above, is to provide flexibility andresilience to a distal end portion of a medical guidewire and to improvethe torque transmission of the medical guidewire.

According to an aspect of the present invention, there is provided amedical guidewire (hereinafter referred to as a “guidewire”) including acore shaft including a distal end portion having a small diameter; anouter flexible tube that surrounds an outer surface of the core shaft; astranded wire disposed parallel to the distal end portion of the coreshaft; and a hollow stranded-wire coil disposed in the outer flexibletube, the hollow stranded-wire coil being formed of multiple strands andsurrounding the distal end portion of the core shaft and the strandedwire. Distal ends of the hollow stranded-wire coil, the core shaft, andthe stranded wire are joined to a distal end of the outer flexible tube.

The strands of the stranded wire can move slightly relative to eachother. Therefore, the stranded wire has a high degree of freedom, a highflexibility, a high resistance to plastic deformation, and a highresilience. Therefore, by disposing the stranded wire parallel to thedistal end portion of the core shaft, the flexibility of the guidewireis maintained and the resilience of the guidewire after being bent intoa U-shape is improved.

The hollow stranded-wire coil, which is formed of multiple strands, isdisposed in the outer flexible tube and surrounds the distal end portionof the core shaft and the stranded wire. The distal ends of the hollowstranded-wire coil, the core shaft, and the stranded wire are joined tothe distal end of the outer flexible tube. The hollow stranded-wirecoil, which is formed of multiple strands, has a better torquetransmission than a single-wire coil. By disposing the distal end of thehollow stranded-wire coil at the distal end of the guidewire in thejoined state, the guidewire can smoothly transmit an operation performedat the proximal end portion to the distal end portion. Therefore, a usercan operate the guidewire at will, so that the treatment time can bereduced. Moreover, the hollow stranded-wire coil has a better resiliencethan a single coil. Therefore, by surrounding outer surfaces of the coreshaft and the stranded wire with the hollow stranded-wire coil, theresilience of the distal end portion of the guidewire can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partially sectional side view of a guidewire according to afirst embodiment;

FIG. 2 is a sectional side view of a distal end portion of the guidewireaccording to the first embodiment;

FIG. 3 is a partial side view of a core shaft of a guidewire accordingto a modification; and

FIG. 4 is a sectional side view of a distal end portion of a guidewireof the related art.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A medical guidewire according to a first embodiment includes a coreshaft including a distal end portion having a small diameter; an outerflexible tube that surrounds an outer surface of the core shaft; astranded wire disposed parallel to the distal end portion of the coreshaft; and a hollow stranded-wire coil disposed in the outer flexibletube, the hollow stranded-wire coil being formed of multiple strands andsurrounding the distal end portion of the core shaft and the strandedwire. Distal ends of the hollow stranded-wire coil, the core shaft, andthe stranded wire are joined to a distal end of the outer flexible tube.

The outer diameter of the core shaft decreases stepwise toward thedistal end. The hollow stranded-wire coil is made by stranding multiplemetal strands. The hollow stranded-wire coil has a tapered shape inwhich the outside diameter gradually decreases toward the distal end.The inside diameter of the hollow stranded-wire coil is uniform from thedistal end to the proximal end. The metal strands of the hollowstranded-wire coil are made of a stainless steel alloy.

First Embodiment Structure of First Embodiment

Referring to FIGS. 1 and 2, the structure of a guidewire 1 according tothe first embodiment will be described. In FIGS. 1 and 2, the right sideis the distal end side, and the left side is the proximal end side. Theguidewire 1 includes a core shaft 2, a stranded wire 3 disposed parallelto the core shaft 2, an outer flexible tube 4 through which the coreshaft 2 and the stranded wire 3 are inserted, and a hollow stranded-wirecoil 5 disposed in the outer flexible tube 4. The core shaft 2 and thestranded wire 3 are inserted through the hollow stranded-wire coil 5.The core shaft 2, the stranded wire 3, and the hollow stranded-wire coil5 are inserted through the outer flexible tube 4.

The core shaft 2 is made of a stainless steel alloy. The core shaft 2has a grip 21, which has a large diameter, positioned adjacent to theproximal end thereof and a distal end portion 22, which has a smalldiameter, positioned adjacent to the distal end thereof. The diameter ofthe distal end portion 22 of the core shaft 2 decreases stepwise. Thedistal end portion 22 of the core shaft includes a step portion 23 and asmall-diameter portion 25 that extends from the step portion 23 to thedistal end of the core shaft 2. In the first embodiment, the outsidediameter of the small-diameter portion 25 is 0.03 mm.

The stranded wire 3 is made by stranding metal strands made of, forexample, a stainless steel alloy. In the first embodiment, for example,the stranded wire 3 is made by stranding seven stainless steel strandseach having an outside diameter of 0.014 mm. The stranded wire 3 isdisposed parallel to the distal end portion 22 of the core shaft 2. Adistal end of the stranded wire 3 and the distal end of the core shaft 2are soldered to a brazed end portion 41 disposed at the distal end ofthe outer flexible tube 4. A proximal end of the stranded wire 3 ispositioned between the proximal end of the small-diameter portion 25 andthe proximal end of the core shaft 2. The proximal end of the strandedwire 3 and the core shaft 2 are soldered to the hollow stranded-wirecoil 5 at a position between the step portion 23 and the proximal end ofthe core shaft 2 (a soldered portion 7).

The outer flexible tube 4 is a single-wire coil made of a stainlesssteel strand. In the first embodiment, for example, the stainless steelstrand has an outside diameter of 0.05 mm and the outer flexible tube 4has an outside diameter of 0.355 mm. In order to provide flexibility tothe distal end portion of the outer flexible tube 4, the pitch of adistal end portion of the outer flexible tube 4 is enlarged. As long asthe outer flexible tube 4 has flexibility, the outer flexible tube 4need not be a single-wire coil and may instead be a hollow stranded-wirecoil, a resin tube, or the like.

The outer flexible tube 4 surrounds only a distal end portion of thecore shaft 2. A proximal end 42 of the outer flexible tube 4 is fixed toan outer surface of a large-diameter portion of the core shaft 2 near tothe proximal end of the core shaft 2. An outer surface of the outerflexible tube 4 is coated with a hydrophilic resin.

The hollow stranded-wire coil 5 is made by stranding multiple stainlesssteel strands around a core by using a wire stranding machine and thenremoving the core, or by stranding multiple strands into a hollow shape.In the first embodiment, for example, the hollow stranded-wire coil 5,which has an outside diameter of 0.188 mm, is formed by stranding sixstainless steel strands each having an outside diameter of 0.04 mm, sothat the flexibility and the torque transmission are well balanced. Adistal end portion 52 of the hollow stranded-wire coil 5 iselectro-polished so that the outside diameter decreases toward thedistal end. The inside diameter of the hollow stranded-wire coil 5 isuniform from the proximal end to the distal end.

The hollow stranded-wire coil 5 has an outside diameter that is smallerthan the inside diameter of the outer flexible tube 4. The hollowstranded-wire coil 5 has a length in the axial direction that is smallerthan that of the outer flexible tube 4. A proximal end 53 of the hollowstranded-wire coil 5 is positioned between the proximal end 42 of theouter flexible tube 4 and the distal end of the outer flexible tube 4 inthe axial direction. The hollow stranded-wire coil 5 and the outerflexible tube 4 are fixed to each other at least one position so thatrelative positions thereof are fixed. In the first embodiment, thehollow stranded-wire coil 5, the outer flexible tube 4, the strandedwire 3, and the core shaft 2 are fixed to each other by soldering at aposition corresponding to the step portion 23 (a soldered portion 8).Moreover, the hollow stranded-wire coil 5 and the outer flexible tube 4are fixed to each other at a position between the proximal end of thestranded wire 3 and the proximal end of the outer flexible tube 4 in theaxial direction (a soldered portion 9).

The proximal end 53 of the hollow stranded-wire coil 5 is positionedbetween the step portion 23 and the proximal end of the core shaft 2 andbetween the proximal end of the stranded wire 3 and the proximal end ofthe core shaft 2. Moreover, as described above, the distal ends of thehollow stranded-wire coil 5, the core shaft 2, and the stranded wire 3are fixed to the brazed end portion 41 at the distal end of the outerflexible tube 4. The proximal end 53 of the hollow stranded-wire coil 5is fixed to the outer surface of the core shaft 2.

Operational Effect of First Embodiment

In the guidewire 1 of the first embodiment, the stranded wire 3 isdisposed parallel to the distal end portion 22 of the core shaft 2. Thediameter of the distal end portion 22 of the core shaft 2 decreasesstepwise toward the distal end. The strands of the stranded wire 3 canmove slightly relative to each other. Therefore, the stranded wire 3 hasa high degree of freedom, a high flexibility, a high resistance toplastic deformation, and a high resilience. Therefore, by disposing thestranded wire 3, which has resistance to plastic deformation, parallelto the distal end portion 22 of the core shaft 2, which has a smalldiameter and thus has flexibility, the resilience of the guidewire 1after being bent into a U-shape is improved while maintaining theflexibility of the guidewire 1.

The guidewire 1 includes the hollow stranded-wire coil 5, which isdisposed in the outer flexible tube 4 and surrounds the distal endportion 22 of the core shaft 2 and the stranded wire 3. The distal endsof the hollow stranded-wire coil 5, the core shaft 2, and the strandedwire 3 are joined to the distal end of the outer flexible tube 4. Thehollow stranded-wire coil 5, which is formed of multiple strands, has abetter torque transmission than a single-wire coil. By joining thedistal end of the hollow stranded-wire coil 5 to the distal end of theouter flexible tube 4 and disposing the distal end of the hollowstranded-wire coil 5 at the distal end of the guidewire 1, the guidewire1 can smoothly transmit an operation performed at the proximal endportion to the distal end portion. Therefore, a user can operate theguidewire 1 at will, so that the treatment time can be reduced.Moreover, the hollow stranded-wire coil 5 has a better resilience than asingle coil. Therefore, by surrounding outer surfaces of the core shaft2 and the stranded wire 3 with the hollow stranded-wire coil 5, theresilience of the distal end portion of the guidewire 1 can be improved.

The distal end portion 52 of the hollow stranded-wire coil 5 has atapered shape in which the diameter gradually decreases toward thedistal end. Therefore, the guidewire 1 has a structure having agradation in rigidity in which the rigidity gradually increases towardthe proximal end, and occurrence of stress concentration due to a sharpdifference in rigidity is suppressed, so that the torque transmission isimproved. The distal end portion of the hollow stranded-wire coil 5 hasa small diameter, so that the flexibility of the guidewire 1 is improvedand the guidewire 1 can be more easily inserted into a peripheral lumen.

The inside diameter of the hollow stranded-wire coil 5 is uniform fromthe distal end to the proximal end. Therefore, the core shaft 2 and thestranded wire 3 can be easily inserted into the hollow stranded-wirecoil 5, so that the guidewire 1 can be easily assembled.

The metal strands of the hollow stranded-wire coil 5 are made of astainless steel alloy. Therefore, the rigidity of the hollowstranded-wire coil 5 is increased, so that the torque transmission andthe operability of the guidewire 1 are improved.

Modification

In the first embodiment, the diameter of the distal end portion 22 ofthe core shaft 2 decreases stepwise toward the distal end.Alternatively, the distal end portion 22 may be tapered toward thedistal end.

In the first embodiment, the core shaft 2 is made of a stainless steelalloy. Alternatively, a part of the core shaft 2 near to the distal end(at least the small-diameter portion 25) may be made of a pseudoelasticalloy having a high resilience (for example, Ni—Ti alloy), and a part ofthe core shaft 2 near to the proximal end may be made of a stainlesssteel alloy. With this structure, the resilience of the distal endportion of the guidewire 1 can be improved, and the torque transmissionand the operability of the guidewire 1 can be improved.

As illustrated in FIG. 3, a part of the small-diameter portion 25 nearto the distal end may be made of a stainless steel alloy (a first distalend portion 26), a part of the small-diameter portion 25 near to theproximal end may be made of a pseudoelastic alloy (a second distal endportion 27), and a part of the core shaft 2 between the small-diameterportion 25 and the proximal end the core shaft 2 may be made of astainless steel alloy. With this structure, the pseudoelastic alloyimproves the resilience of the distal end portion 22 of the core shaft2. Moreover, because the portions made of a stainless steel alloy areprovided to both sides of the part made of a pseudoelastic alloy (thesecond distal end portion 27), a torque applied to the proximal endportion of the guidewire 1 can be reliably transmitted to the distal endportion, so that the torque transmission and the operability of theguidewire 1 can be further improved.

In the first embodiment, the distal end portion 52 of the hollowstranded-wire coil 5 is tapered toward the distal end. Alternatively,the diameter of the distal end portion 52 may decrease stepwise towardthe distal end.

In the first embodiment, the hollow stranded-wire coil 5 is made of onlystainless steel strands. Alternatively, the hollow stranded-wire coil 5may be made of only pseudoelastic alloy strands. With this structure,the resilience of the hollow stranded-wire coil 5 can be furtherincreased. As a further alternative, the hollow stranded-wire coil 5 maybe formed by combining stainless steel strands and pseudoelastic alloystrands (for example, three stainless steel strands and threepseudoelastic alloy strands). In this case, the stainless steel strandsincrease the rigidity of the hollow stranded-wire coil 5, while thepseudoelastic strands increase the resilience of the hollowstranded-wire coil 5. Therefore, the torque transmission, theoperability, and the resilience of the guidewire 1 are improved.

In the first embodiment, the outer flexible tube 4 surrounds only thedistal end portion of the core shaft 2. Alternatively, the outerflexible tube 4 may surround the entirety of the core shaft 2.

The present invention contains subject matter related to Japanese PatentApplication No. 2009-143570 filed in the Japan Patent Office on Jun. 16,2009, the entire contents of which are incorporated herein by reference.

1. A medical guidewire comprising: a core shaft including a distal endportion having a small diameter; an outer flexible tube that surroundsan outer periphery of the core shaft; an inner flexible tube disposed inthe outer flexible tube, the inner flexible tube surrounding the distalend portion of the core shaft; a first joint that joins a distal end ofthe core shaft, a distal end of the outer flexible tube, and a distalend of the inner flexible tube to one another; and at least one secondjoint that does not join the core shaft and joins the outer flexible tothe inner flexible tube.
 2. The medical guidewire according to claim 1,further comprising: a stranded wire disposed parallel to the distal endportion of the core shaft in the inner flexible tube between the secondjoint and the distal end of the core shaft.
 3. The medical guidewireaccording to claim 1, wherein the inner flexible tube has a taperedshape in which an outside diameter gradually decreases toward the distalend thereof.
 4. The medical guidewire according to claim 1, wherein anoutside diameter of the inner flexible tube decreases stepwise towardthe distal end thereof.
 5. The medical guidewire according to claim 3,wherein an inside diameter of the inner flexible tube is uniform fromthe distal end to a proximal end thereof.
 6. The medical guidewireaccording to claim 4, wherein an inside diameter of the inner flexibletube is uniform from the distal end to a proximal end thereof.
 7. Themedical guidewire according to claim 1, wherein the inner flexible tubeis a hollow stranded-wire coil in which a plurality of metal strands arestranded.
 8. The medical guidewire according to claim 1, wherein theouter flexible tube is a single-wire coil including a large-pitchportion extending from the distal end of the outer flexible tube towarda proximal end of the outer flexible tube by a predetermined distance,the large-pitch portion having a pitch that is larger than a pitch of aproximal end portion of the outer flexible tube, and wherein a proximalend of the large-pitch portion is positioned between the second jointand the distal end of the outer flexible tube.